Process for drawing and crimping yarn



Aprii 1968 D. w. WOODS 3,379,869

PROCESS FOR DRAWING AND CRIMPING YARN Filed March 25, 1966 SPUA/ VHF/V W/Afi- 0, 5065/ INVENTOR.

DEW/5 MAL/6M7 14 0005 ATTORNEYS United States Patent 3,379,809 PROCESS FOR DRAWING AND CRIMPING YARN Denis William Woods, Harrogate, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Continuation-impart of abandoned application Ser. No. 240,092, Nov. 26, 1962. This application Mar. 25, 1966, Ser. No. 537,553 Claims priority, application Great Britain, Nov. 24, 1961, 42,101/ 61 12 Claims. (Cl. 264-168) This is a continuation-in-part of my earlier application Ser. No. 240,092, filed Nov. 26, 1962, and now abandoned.

This invention relates to a process for simultaneously drawing and crimping filaments made from fibre-forming polymers.

I have made the unexpected and surprising observation that useful crimped filaments may be obtained in a drawing process under carefully selected conditions and provided that the filaments are not reheated when under drawing tension i.e. after leaving a snubbing pin and before being wound up after drawing. This surprising observation has been made when investigating drawing conditions similar to those described in British Patent 903,027.

Man other processes for the drawing of yarns from fibre-forming polymers are known. One such process is described in US. Patent 2,533,013 involving drawing a synthetic filament forming material in two stages, comprising a heated, nonrotatable snubbing pin and a heated surface. Another process comprises the steps of feeding yarns from a cold roller on to and around a roller which is heated to a temperature of at least 60 0., preferably 75 to 100 and which is running with a peripheral speed sufliciently great as to effect the required degree of extension, as described in British Patent 603,843. Yet another process is described in Canadian Patent 590,347 comprising feeding the yarn to an unheated feed roller, then passing it around another roller which has been heated to a temperature of 60 C. to 200 C. and rotates at substantially the same peripheral speed, wrapping the yarn, after it has left the hot roller one quarter to at least one time around a stationary unheated pin and finally passing it around a drawing roller the speed of which is a multiple of that of the heated roller. In none of the prior art specifications discussed above has there been any suggestions that a crimped yarn or filament may be obtained in these drawing processes.

However, many processes for the manufacture of crimped yarns are known, comprising passing the yarn over a de-forming edge as described e.g. in British specification 558,297 or over a narrow heated surface without stretching the yarn more than as described in British Patent 808,213.

In the prior art specifications relating to these crimping processes by passing the yarn over a deforming edge as well as those comprising stretching the yarn while passing over a narrow heated surface but without drawing, where- 'by a temperature gradient is imparted across the filaments, no drawing of the filaments takes place. Moreover filaments which are crimped by imparting a temperature gradient contain latent crimp, which can be brought out by heating the filaments in a relaxed condition.

In US. Patent 3,101,990 there is disclosed a process in which yarn is stretched over a heated shoe and then drawn in a snubbing zone. The snubbing zone and the shoe may be in contact and are heated to about the same temperature, between the second order transition temperature and 45 C. above. It is stated that the yarn 3,379,809 Patented Apr. 23, 1968 produces a spontaneous crimp When the snubbing zone is a pin whose diameter is less than 7 inch, e.g. inch, but that uncrimped yarn is obtained when the pin diameter is to inch.

I now provide a more versatile process which imparts a novel type of crimp t-o filaments made from synthetic linear polymers during a modified drawing operation. The crimp becomes almost instantaneously apparent on relaxing the filaments from tension at room temperature, without further heating. My process can be operated at high speeds and because it forms an integral part of a drawing process, it is economical and can be operated with inexpensive modifications of existing drawing and other equipment as used in the manufacture of synthetic filament yarns and staple fibres.

The filaments for use in my process must be capable of being cold drawn, showing the formation of a characteristic neck and shoulder between the drawn and undrawn portion of the filaments, and they should have a natural draw ratio at room temperature making them capable of being elongated at least twice their length, as spun.

According to my invention I provide a rapid integrated process for the manufacture of crimped filaments and fibres from undrawn melt spun filaments having a natural draw ratio at room temperature making them capable of being elongated at least twice their length and which, in the case of filaments melt spun from polyethylene terephthalate, have an intrinsic viscosity between 0.4 and 0.7 and an optical birefringence between 0.001 to 0.015, both sets of figures inclusive, comprising drawing the filaments 2.5 to 6 times their length between feed rolls and draw rolls, introducing a tension gradient and localizing the draw zone with a snubbing pin interposed between said rolls, heating the filaments in a 1st zone maintained close to and before the snubbing pin, at a temperature between 15 C. and 450 C. about the 2nd order transition temperature of the polymer from which the filaments are made, C. to C. in the case of polyethylene terephthal ate filaments, passing the heated filament-s without allowing them to cool substantially and so that stretching is limited to less than 20% and without drawing, to a small snubbing pin capable of being internally heated and maintained at a selected temperature, in close proximity to said 1st zone, maintaining said snubbing pin at a temperature between about 85 C. above the second order transition temperature and 30 C. above the melting temperature of the filaments, i.e. C. to 295 C. for polyethylene terephthalate, said snubbing pin having a radius of curvature less than 6 mm. and as small as is consistent with mechanical requirements and providing a surface and an arc of contact capable of imparting a tension gradient such that substantially all the drawing takes place on the snubbing pin and between it and the draw rolls but close to the snubbing pin and without reaching the draw rolls and while the filaments are spread into a ribbon so that they become heated from the surface of the snubbing pin, when making an arc of contact of at least 90 and up to four .turns around the pin, passing the filaments to the draw rolls rotating at a speed to provide sufficient tension to draw the filaments to the required draw ratio and at a speed of at least 1,000 ft. per minute, forwarding the filaments under a tensionle-ss than the drawing tension and subsequently relaxing the filaments at least 70% at room temperature, without any intermediate heating to a temperature above the second order transition temperature to show their full crimp of at least four crimps per inch and a crimp elongation of at least 70%, solely as a result of the specified drawing process.

The following detailed description and the examples illustrate my invention by reference to filaments melt spun from polyethylene terephthalate, but I believe that my invention is applicable to filament yarns and tows of other polymers particularly those derived from terephthalic acid as well as the polyamides which have a natural draw ratio and a melting temperature of the same order as those of polyethylene terephthlate.

The birefringence of the undrawn polyethylene terephthalate filaments should be between 0.001 to 0.015, preferably 0.005 to 0.015 the intrinsic viscosity of the undrawn filaments should be between 0.4 and 0.7, preferably between 0.42 and 0.47 for manufacture of fibres for use in spun yarn fabrics where a reduced tendency to pilling is required, and between 0.58 and 0.65 for textile applications where a high abrasion resistance is required. A circular cross-section of the filaments may be used of a denier between 3 and 12 per filament and 1 to 50 filaments in filament yarns. Tow-s may also be processed according to my invention provided that the contact angle with the snubbing pin is about 180 or less but more than 90 of are of contact, on the snubbing pin.

Greater arcs of contact are advantageous if they can be used, as in the case of filament yarns when up to 4 complete turns around the snubbing pin can be made. Generally therefore, the are of contact of the filaments with the snubbing pin should be greater than 90 and up to 144 preferably about 180 to 360 i.e. to one complete turn around the pin.

The filaments on passing over or around the snubbing pin spread into a ribbon, if twistless yarns r tows are used, but a certain amount of crossing over of the filaments, as may be caused by a small amount of twist is not detrimental and in some cases may help to bring about or maintain a useful relative displacement in the crimped filaments.

If the 1st zone consists of a curved circular cylindrical rotating surface or roll, the distance between it and the snubbing pin, expressed as the free tangential distance of the filament path is preferably 2 to 8 cm, which gives a useful crimp, although, as appears in the data which follows, greater distances may be used, e.g. 16 cm.

I have found that the drawing speeds are quite critical and no useful crimp is obtained at speeds below 1,000 feet per minute for the above deniers. Useful speeds giving a good crimp and useful runability are between 2,000 and 4,000 feet per minute.

The lst zone for heating the filaments prefer-ably consists of the feed rolls themselves, adequate heating being obtained by lapping the yarn a sufiicient number of turns around one or more heated roll-s. Converse-1y it may be possible to heat the filaments beyond the feed rolls for example by cont-act with an electrically heated plate or some other suitable heating means which is amenable to an accurate heat control as disclosed in British Patent 903,027. I have found temperature variations in the 1st zone to have a profound effect on the crimp obtained and no useful crimp is obtainable at temperatures only 2 below 95 C. whereas at 95 to 106 C. useful crimp results, under conditions specified hereafter.

The 2nd heating zone comprising the snubbing pin has the function of imparting a tension gradient to the filaments between the feed rolls and the draw rolls and it is essential that substantially all the drawing occurs either on or just beyond the snubbing pin in that zone. The relative positioning of the two zones is also important and they should be as close together as possible and in order that no substantial cooling takes place between the 1st zone and the snubbing pin in the 2nd zone. Preferably the distance does not exceed 10 cm.

The material from which the snubbing pin is made should withstand not only abrasion and the mechanical strains from the contacting filaments but also the temperature and include means for heating and controlling the temperature, which in my examples have been measured by a thermo-couple in the centre of the pin, because I have found it impossible to measure the temperature on the surface of the snubbing pin in contact with the movin filaments. Ceramic material which is commercially available under the trade marks Faradex and Syntox has been found mechanically suitable. It can be drilled or otherwise be made hollow for the insertion of suitable heater elements, thermo-couples or other thermo-sensing means. It will be appreciated that metallic pins with a hard wearing coating including a ceramic coating or a sand blasted chromed surface may also be used, provided that the surface is evenly cured, preferably cylindrical and evenly dulled or smooth and which will fulfill the stated requirements. It should be noted that all temperatures given in this specification relate to a ceramic snubbing pin. Since the measurements are made inside and not on the surface of the pin they will be considerably lower than if a metal pin were used.

An important advantage of the present invention is the possibility of using larger diameter snubbing pins. Whereas US. Patent 3,101,990 indicates uncrimped yarn is obtained when the snubbing pin diameter is larger than 33 inch (4.75 mm.) I can obtain a crirnped yarn with larger pins, e.g. having a diameter greater than 5 mm., particularly where the diameter is about 5.5 to 12 mm.

The surface of the snubbing pin, the coefficient of friction with the filaments, the arc of contact with the filaments and other conditions should be chosen so that there is a tension gradient on the snubbing pin, which is located between the feed and draw-rolls, and so that there is a greater tension in the thread line leaving the snubbing pin than in the portion approaching it. If the tension in the thread line before the snubbing pin is greater than when leaving it, no crimp or no useful crimp is obtained. The tension between the feed rolls and/ or the first heated zone and between it and the second zone should therefore be such that stretching is limited to less than 20% and insufficient to effect drawing of the filaments before reaching the snubbing pin. If this is not done the draw zone may run back to the feed roll and no useful crimp is obtained and running conditions are unstable.

Generally the temperature in the snubbing pin may be up to 290 C. when measured at the center of the pin in the case of polyethylene terephthalate filaments, bearing in mind that there is a temperature gradient from the center to the surface of the pin, and that the filaments do not necessarily become heated to the temperature measured and attained at the center of the pin.

The diameter of the snubbing pin has a profound effect on the crimp obtained and it should be chosen depending on the filament denier and the number of filaments passing over it and consistent with mechanical requirements. Lower deniers, fewer filaments and lower speeds make the use of small diameter snubbing pins possible and desirable. Circular cylindrical snubbing pins of diameters 1 to 10 mm. may be used and those of 1.5 to 6.5 mm. are preferred. However, as indicated above, one of the advantages-of the high temperature used for the pin is the possibility of using larger diameter pins, e.g. about 5.5 to 12 mm. diameter (that is, having a radius of curvature of about 2.75 to 6 mm).

It should be appreciated that the snubbing pin becomes heated by frictional contact with the filaments and that under certain conditions no internal heating may be necessary, to achieve the required temperature. However, heat ordinarily is applied.

On leaving the snubbing pin the filaments or yarns are taken up by the draw rolls, rotating at a linear speed between 3 and 6 times that of the feed rolls and to give the required draw ratio. In the case of yarns the filaments may be lapped around the draw rolls with associate idler roll in several turns or nip rolls or a set of draw rolls or a combination of these may be used, if desired. From the draw rolls the yarn may be forwarded to forwarding rolls for further processing, or they may be wound up on suitable packages using the conventional winding tensions of about 0.2 gram per denier.

The imparted crimpbecomes apparent when the filaments are released from tension e.g. when they are unwound from the yarn package. In this connection it is interesting to note that the imparted crimp is permanent and does not change with the passage of time. I have found that filament yarn processed according to my invention when wound up and stored on bobbins for 4 months, have the same amount of crimp as when first wound up.

On heating a single filament with dry heat or steam at heat setting temperatures or even on immersion in boiling water, the filaments uncurl and substantially all the crimp is lost. However if care is taken that a number of crimped filaments are so heated in a relaxed condition in such a way that there is a relative displacement of the crimped filaments and cohesion between the filaments it is found that uncoiling is prevented and a configuration similar to the imparted crimp is not only retained but permanently set in the filaments, which then withstand further heating at temperatures slightly below the setting temperature, without losing the imparted crimp-deformations.

The process is not clearly understood but it appears that crimping may be a combination of a heat setting, deforming and temperature gradient process which however operates under conditions which are not obtainable if the process were not used during drawing of the filaments. During drawing at least under my specified conditions complex changes are brought about in the filaments resulting in a desirable crimp and other desirable properties, the combination of which is novel. In the examples and tables that follow an attempt has been made to determine the experimental conditions which are required to obtain an acceptable crimp in the filaments. These conditions are quite critical.

The following examples illustrate but do not limit my invention.

Example 1 This example, and Table 1, illustrates the effect of distance between the snubbing pin and the hot feed roll at intervals from 2 to 16 cm. It will be seen that a crimp is obtained only at distances of 2, 4 and 8 em, if the temperature of the pin is between 84 and 88 C.; on the other hand, if the temperature of the pin is further increased to 170 C. the versatility of the process also is increased and a useful crimp is obtained over the whole range of distances of 2 to 16 cm. between the feed rolls and the snubbing pin.

However, if the temperature of the feed rolls is too low, even if the snubbing pin temperateure is increased to 174 C., no useful crimp is obtained at a distance of 1 6 cm., equally no useful crimp is obtained if the temperature of the pin is reduced to 80 C. Whether the temperature of the rolls is 100 C. or 84 C., as shown in Table 1.

Example 2 This example, and Table 2, illustrates the effect of the arc of contact of the filaments on the snubbing pin. It will be seen that an arc of contact up to and including 90 yield no crimp or only a slight crimp of 4 crimps per inch at a roll surface temperature of 100 and a snubbing pin temperature of 170 C. Good results are obtained, however, with an arc of contact of 180 (1 half turn and 1 whole turn, 1% turns and even 2 turns round the pin), at these temperatures. The first three experiments in Table 2 also show that low pin temperatures prevent crimping.

Example 3 This example, and Table 3, illustrates the effect of the diameter of the snubbing pin from 1.6 to 9.5 mm. It will be seen that the smaller the pin the more versatile the conditions become under which a crimp is obtained. In contrast, when the pin diameter is increased, a crimp is only obtained with the high pin temperature of this invention. Table 3 also illustrates that at a snubbing pin temperature of 61 C. no useful crimp results, if the hot roll surface is 99 C., but if the temperature of the snubbing pin is raised to 170 C. under the same conditions a crimp is obtained.

Example 4 This example, and Table 4, is an attempt to determine the temperature for the snubbing pin using the roll surface temperature of 100 C. and a relatively small snubbing pin as in the previous examples of 5.2 mm. diameter and 1 turn on the snubbing pin, at a distance of 2 cm. between the snubbing pin and the feed rolls, at a draw speed of 3,000 ft. per minute. It will be seen that a crimp is obtained at temperatures of up to 290 C., bearing in mind that the temperature is measured inside the snubbing pin and that this is not necessarily an indication of the temperature on the surface contacting the filaments. It will be seen that under these conditions the crimp extension is already falling off to 138% at 290 C. If at approximately the same temperature, namely 280 C., the roll surface temperature is dropped to 22 C., no crimp is obtained and the filaments are straight. It therefore appears that the upper temperature limit for the snubbing pin under these conditions is about 30 C. above the melting temperature of the filaments.

Example 5 This example, and Table 5, illustrates in greater detail the effect of the arc of contact on the tension gradient across the snubbing pin. The roll surface temperature used is C. It will be seen that a tension ratio greater than 0.9 to 1 is required to result in crimped filaments. In other words, drawing should take place on the snubbing pin, or between it and the draw rolls, as a result of a tension gradient on the pin.

From the preceding examples and the description it will be apparent that (i) High drawing speeds can be used and speeds above 1,000 feet per minute are in fact essential.

(ii) Even low delicate yarn deniers may be processed as well as heavy tows.

(iii) The process is an integration with a necessary drawing process.

(iv) A stable crimp is produced when the filaments are relaxed at room temperature, without further heating.

(v) The process can be operated on existing equipment using a ceramic snubbing pin beyond and near to a hot feed roll system. This and the above features make the process technically and commercially desirable.

In the examples, unless otherwise stated, the following details of the yarn and the process used apply.

(a) Polyethylene terephthalate melt spun unclrawn yarn Intrinsic viscosity 0.65 Undrawn denier Number of filaments 24 Birefringence 0.00 8 Spin finishan aqueous dispersion of a mineral 'oil, percent on weight of fibres 1 /2 (b) The drawing process Stretch applied before feed rolls percent 0.5 Number of turns on hot feed roll 4 Diameter of hot feed roll inches 4 Draw ratio 3.3:1 Drawn yarn wind-up tension g./d 0.25 Snubbing pin diameter rnm 5.2 Contact angle of snubbing (1 turn) degrees 360 Distance between hot roll and snubbing pin (tangential distance of thread line 2 cm. (2,4, 8,16 cm. in Table 4)). Draw speed ft./-min 3,000

The attached figure is a diagrammatic illustration of one form of our apparatus as used for the examples with pretensioning rolls, 1, 2 feed rolls, 3, 3A the snubbing in 4, the draw rolls 5 and idler rolls 3A and 5A associated with the feed and draw rolls.

Referring to the figure undrawn yarn coming from a yarn supply, spun yarn bobbin, is unwound over-end and taken via a guide to the pre-tensioning roll 1 with nip roll 2 to the feed rolls 3 with associated idler 3A. Four turns are made round these rolls, roll 3 being heated as necessary with means for measuring and maintaining the temperature at /2 C. From the feed roll 3 the yarn, which is lightly pre-tensioned by the rolls 1 and 2 is looped a required amount round the ceramic snubbing pin 4 and then to faster rotating draw rolls 5 and 5A, before being wound up under light Winding tension on a Windup bobbin. The snubbing pin is provided with an internal heater and temperature measuring and controlling means.

It is interesting to note that my process does not seem to result in crimped filaments if instead of undrawn filaments drawn filaments of polyethylene terephthalate are used.

I claim:

1. A rapid integrated process for the manufacture of crimped filaments and fibers having low shrinkage and high crimp extension from undrawn melt spun polyester filaments having a natural draw ratio at room temperature making them capable of being elongated at least twice their length,

comprising drawing the filaments 2.5 to 6 times their length between feed rolls and draw rolls,

introducing a tension gradient and localizing the draw 10 zone with a small snubbing pin interposed between said rolls,

heating the filaments in a first zone maintained close to and before the snubbing pin, at a temperature between 15 C. C. above the second order transisition temperature of the polymer from which the filaments are made,

TABLE 1.-EFFECT OF DISTANCE BETWEEN SNUBBING PIN AND HOT FEED ROLL Temperature, C. Crimps Distance, cm. Shrinkage, Ext., Ten., Crimp per Appearance Roll Pin percent percent gJd. ext. inch Surface 100 8.9 29 4.0 115 4 to 15..-- Crimp, 100 88 92 D0. 100 84 10. 6 31 3. 9 101 100 80 12.3 33 3.9 69 84 60 7 100 170 7.0 31 3.8 98 5 to 13 Crimp. 100 170 7. 2 30 4. 0 102 D0. 100 170 7.8 34 4. 1 163 9 to 19 Do. 93 174 10.8 31 4. 3 34 Wavy. 84 170 12.0 30 4.4 4 Straigh TABLE 2.EFFECT 0F ARC OF CONTACT ON SNUBBING PIN Temperature, 0, Shin, Ext, Ten, Crimp Crimps Arc of contact perperg.]d. ext, per Appearance Roll surface Pin cent cent per cent inch 100 14.7 28 4.1 5 Straight. 100 54 14. 0 23 4. 0 2 0. 7 Slightly wavy. 100 11. 3 24 4.3 28 Wavy. 170 9.1 31 4.2 8 1. 3 o. 100 170 9.2 22 4.1 81 4 Slight crimp. 100 168 7.8 26 4.3 134 Crimp. 100 168 7. 0 26 4. 1 170 Do. 100 170 6. 8 25 4. 3 203- 9 Do. 100 170 6. 1 25 4. 2 Do.

TABLE 3.EFFECT OF SNUBBING PIN DIAMETER Temperature, C. Shr., Ext., Ten, Crimp Crimps Pin diam, mm. perpergJd. e per Appearance Roll surface Pin 1 cent cent per cent inch 99 102 7.6 35 4.2 116 Crimp. 99 98 9. 1 35 4.6 128 Do. 99 91 9.9 31 4.4 151 Do. 99 87 9.9 31 4.3 106 Slight crimp. 99 61 12. 3 28 4. 2 l4 (1) Wavy. 99 176 Crnnp.

TABLE 4.-EFFECT 0F SNUBBING PIN TEMPERATURE Temperature, C. Shn, Ext, Ten., Crimp Crimps Percent Percent g./d. ext., per inch Appearance Roll surface Pin Percent 100 85 10.6 26 4 3 115 Crimp. 100 170 7.1 22 3.6 98 Do. 100 226 5. G 22 3. 7 216 10 D0. 100 265 5. 5 21 3. 4 164 Do. 100 274 D0. 100 290 138 D0. 100 300 }Frequent laps cause threadline 100 310 breakdown.

22 280 6.6 Straight.

TABLE 5.EFFECT OF ARC OF CONTACT ON TENSION 6 v) GRADIENT ACROSS PEG a Is 0.36 using results for 180, 360 and 720 arcs of contact.

passing the heated filaments without allowing them to cool substantially and so that stretching is limited to less than 20% and without drawing, to said snubbing pin, which is capable of being internally heated and maintained at a selected temperature, in close proximity to said first zone, maintaining said snubbing pin at a temperature between 85 C. above the second order transition temperature and 30 C. above the melting temperature of the filaments, said snubbing pin having a radius of curvature less than 6 mm. and as small as is consistent with mechanical requirements and providing a surface and an arc of contact capable of imparting a tension gradient such that substantially all the drawing takes place on the snubbing pin and between it and the draw rolls but close to the snubbing pin and without reaching the draw rolls and while the filaments are spread into a ribbon so that they become heated from the surface of the snubbing pin, when making an arc of contact of at least 180 and up to four turns around the pin, passing the filaments to the draw rolls rotating at a speed to provide sufficient tension to draw the filaments to the required draw ratio and at a speed of at least 1,000 ft. per minute,

forwarding the filaments under a tension less than the drawing tension,

and subsequently relaxing the filaments at least 70% at room temperature, without any intermediate heating to a temperature above the second order transition temperature to show their full crimp of at least four crimps per inch and a crimp elongation of at least 70%, solely as a result of said drawing process.

2. A process for the manufacture of crimped filaments and fibers as set forth in claim 1 in which the filament is melt spun from polyethyleneterephthalate of an intrinsic viscosity between 0.4 and 0.7 and an optical birefringence between 0.001 and 0.015, both sets of figures inclusive and the temperature in the first zone is 95 to 125 C.

3. A process for the manufacture of crimped filaments and fibers as set forth in claim 1 in which the first zone is a curved stationary surface, and the temperature in the first zone is between 45 C. above the second order transition temperature and 30 C. above the melting temperature of the filaments.

4. A process for the manufacture of crimped filaments and fibers as set forth in claim 1 in which the filaments are melt spun from polyethylene terephthalate having an intrinsic viscosity between 0.58 and 0.65.

5'. A process according to claim 1 for the manufacture of crimped fibers in which the filaments are melt spun from polyethylene terephthalate of an intrinsic viscosity between 0.42 and 0.47.

6. A process according to claim 1 in which the filaments are of circular cross-section and of a denier between 3 and 12.

7. A process according to claim 1 in which the arc of contact of the filaments with the snubbing pin is to 360.

8. A process according to claim 1 in which the first zone consists of a curved circular cylindrical surface, the distance between said surface and said snubbing pin expressed as a free tangential distance of the filament path being 2 to 8 cm.

9. A process according to claim 1 in which the drawing speed is between 2,000 and 4,000 ft. per minute.

10. A process according to claim 1 in which the snubbing pin used has low heat conductivity and is made of a ceramic material having a surface which with a suitable arc of contact provides a tension gradient with the filaments so that there is a greater tension in the thread line leaving the snubbing pin than in the portion approaching it.

11. A process according to claim 1 in which the snubbing pin has a diameter of 1.5 to 6.5 mm.

12. A process according to claim 1 in which the filaments are wound up on a suitable package using a winding tension of 0.1 to 0.3 gram per denier.

References Cited UNITED STATES PATENTS 3,093,444 6/1963 Martin 264168 3,101,990 8/1963 Heighton 264290 3,226,792 1/ 1966 Starkie et al 264-290 3,112,551 12/ 1963 Schmiede et a1.

JAMES A. SEIDLECK, Primary Examiner.

J. WOO, Assistant Examiner. 

1. A RAPID INTEGRATED PROCESS FOR THE MANUFACTURE OF CRIMPED FILAMENTS AND FIBERS HAVING LOW SHRINKAGE AND HIGH CRIMP EXTENSION FROM UNDRAWN MELT SPUN POLYESTER FILAMENTS HAVING NATURAL DRAW RATIO AT ROOM TEMPERATURE MAKING THEM CAPABLE OF BEING ELONGATED AT LEAST TWICE THEIR LENGTH, COMPRISING DRAWING THE FILAMENTS 2.5 TO 6 TIMES THEIR LENGTH BETWEEN FEED ROLLS AND DRAW ROLLS, INTRODUCING A TENSION GRADIENT AND LOCALIZING THE DRAW ZONE WITH A SMALL SNUBBING PIN INTERPOSED BETWEEN SAID ROLLS, HEATING THE FILAMENTS IN A FIRST MAINTAINED CLOSE TO AND BEFORE THE SNUBBING PIN, AT A TEMPERATURE BETWEEN 15*C.-45*C. ABOVE THE SECOND ORDER TRANSISITION TEMPERATURE OF THE POLYMER FROM WHICH THE FILAMENTS ARE MADE, PASSING THE HEATED FILAMENTS WITHOUT ALOWING THEM TO COOL SUBSTANTIALLY AND SO THAT STRETCHING IS LIMITED TO LESS THAN 20% AND WITHOUT DRAWING, TO SAID SNUBBING PIN, WHICH IS CAPABLE OF BEING INTERNALLY HEATED AND MAINTAINED AT A SELECTED TEMPERATURE, IN CLOSE PROXIMITY TO SAID FIRST ZONE, MAINTAINING SAID SNUBBING PIN AT TEMPERATURE BETWEEN 85*C. ABOVE THE SECOND ORDER TRANSITION TEMPERATURE AND 30*C. ABOVE THE MELTING TEMPERATURE OF THE FILAMENTS, SAID SNUBBING PIN HAVING A RADIUS OF CURVATURE LESS THAN 6 MM. AND AS SMALL AS IS CONSISTENT WITH MECHANICAL REQUIREMENTS AND PROVIDING A SURFACE AND AN ARC OF CONTACT CAPABLE OF IMPARTING A TENSION GRADIENT SUCH THAT SUBSTANTIALLY ALL THE DRAWING TAKES PLACE ON THE SNUBBING PIN AND BETWEEN IT AND THE DRAW ROLLS BUT CLOSE TO THE SNUBBING PIN AND WITHOUT REACHING THE DRAW ROLLS AND WHILE THE FILAMENTS ARE SPREAD INTO A RIBBON SO THAT THEY BECOME HEATED FROM THE SURFACE OF SNUBBING PIN, WHEN MAKING AN ARC OF CONTACT OF AT LEAST 180* AND UP TO FOUR TURNS AROUND THE PIN, PASSING THE FILAMENTS TO THE DRAW ROLLS ROTATING AT A SPEED TO PROVIDE SUFFICIENT TENSION TO DRAW THE FILAMENTS TO THE REQUIRED DRAW RATIO AND AT A SPEED OF A LEAST 1,000 FT. PER MINUTE, FORWARDING THE FILAMENTS UNDER A TENSION LESS THAN THE DRAWING TENSION, AND SUBSEQUENTLY RELAXING THE FILAMENTS AT LEAST 70% AT ROOM TEMPERATURE, WITHOUT ANY INTERMEDIATE HEATING TO A TEMPERATURE ABOVE THE SECOND ORDER TRANSITION TEMPERATURE TO SHOW THEIR FULL CRIMP OF AT LEAST FOUR CRIMPS PER INCH AND A CRIMP ELONGATION OF AT LEAST 70%, SOLELY AS A RESULT OF SAID DRAWING PROCESS. 